Method for reducing erosion and corrosion of metal surfaces

ABSTRACT

EROSION AND CORROSION OF METAL SURFACES EXPOSED TO A FLOWING STREAM OF HOT GASES CONTAINING DISPERSED PARTICLES OF SOLID MATERIAL ARE REDUCED BY INTRODUCING INTO THE FLOWING STREAM AN ADDITIVE THAT DECOMPOSES AT THE TEMPERATURE AND PRESSURE OF THE GAS TO RELEASE AMMONIA OR A VAPOROUS AMINE AND FORM A RESINOUS RESIDUE. THE ADDITIVE IS PREFERABLY INTRODUCED INTO THE GAS IN AN INERT CARRIER LIQUID.

United States Patent US. Cl. 212.5 R 13 Claims ABSTRACT OF THEDISCLOSURE Erosion and corrosion of metal surfaces exposed to a flowingstream of hot gases containing dispersed particles of solid material arereduced by introducing into the flowing stream an additive thatdecomposes at the temperature and pressure of the gas to release ammoniaor a vaporous amine and form a resinous residue. The additive ispreferably introduced into the gas in an inert carrier liquid.

This is a division of application Ser. No. 44,661 filed June 8, 1970,now issued as Pat. No. 3,653,452.

This invention relates to inhibiting erosion and corrosion of metalsurfaces, and more particularly to inhibiting erosion and corrosion ofmetal surfaces exposed to a hot flowing gas containing dispersedparticles of solid material. This invention further relates to reducingerosion and corrosion of drill pipe employed in gas drilling wells intohigh-temperature subterranean formations, and especially in the gasdrilling of wells into steam-bearing formations.

Substantial erosion and corrosion of metal drill pipe is oftenexperienced when gas drilling into high-temperature subterraneanformations. In gas drilling, air, nitrogen, natural gas, or othergaseous fluids are utilized as the drilling fluid. The gas is passedfrom the surface downwardly through the drill pipe, outwardly through arotary bit attached to the lower end of the drill pipe, and thenupwardly through the annulus on the exterior of the drill pipe at apressure and volumetric flow rate sufficient to cool the bit and liftthe particulate drill bit cuttings to the surface, but which are notsufliciently high as to cause fracturing of the formation.

Gas and entrained solid cuttings pass upwardly through the well annulusat velocities which are typically between and 100 feet per second, orhigher. The particles of solid material transported at these gasvelocities are highly abrasive. Also, high temperatures are oftenencountered. Bottomhole temperatures above about 300 F. are not unusual,and are sometimes in excess of 500 F. These conditions, combined withthe corrosive brines, sulfurous compounds and oxygen which are oftenpresent in the bore hole, are conducive to excessive erosion andcorrosion of the drill pipe, casing and other metal parts. The lifeexpectancy of drill pipe employed under these conditions is relativelyshort, requiring frequent inspection and replacement. Furthermore, aneven more serious problem is the failure of the drill pipe in servicewherein the drill pipe breaks leaving a lower section of the drill pipein the well. Drill pipe failures interrupt the drilling operation, oftenrequiring expensive fishing operations to recover the pipe remaining inthe well, and on occasion, if the fishing operation is not successful,necessitate abandonment of the well.

The problems associated with gas drilling are further accentuated whendrilling into steam-bearing strata, such as are encountered indeveloping geothermal reservoirs. Not only are the temperatures of thesestrata generally above about 500 F., but also steam enters the well fromthe surrounding strata increasing the velocity of the gas passingupwardly in the well annulus to as high as sonic velocities, whichfurther increases the erosion of the metal surfaces exposed to thesolids-containing gas. The intrusion of steam into the well seriouslypromotes drill pipe erosion and corrosion, and in many instances thepresence of steam is so detrimental that gas drilling becomesimpractical requiring the use of slower and more costly techniquesemploying liquid or mud-type drilling fluids.

Various techniques for ameliorating the problems associated with highvelocity, solids carrying gas streams have been attempted. Most of thiseffort, however, has been restricted to changing the performancecharacteristics of the metal parts exposed to the flowing stream. Forexample, it has been proposed to make the metal parts thicker, therebyprolonging the life of the part, or alternatively to harden the metalsurface by heat treating, or with special alloys, and. to introducecorrosion inhibitors into the flowing stream to at least reducecorrosion. In gas drilling, it has been proposed to reduce thecirculating gas velocity by incorporating foaming agents into thedrilling gas. However, these techniques are costly and at best are onlymarginally effective. Thus, need exists for an inexpensive method forreducing erosion and corrosion of metal surfaces contacted by arelatively hightemperature, high-velocity, solids-carrying gas stream.

Accordingly, it is a principal object of this invention to provide amethod for reducing erosion and corrosion of metal surfaces exposed to aflowing gas stream containing dispersed solid particles. It is anotherobject of the invention to provide a method for reducing erosion andcorrosion of metal surfaces exposed to a flowing stream of relativelyhigh-temperature gas and dispersed solid abrasive particles. Otherobjects and advantages of the invention will be apparent to thoseskilled in the art from the description thereof which follows.

The aforementioned objects and their attendant advantages can berealized by introducing into the flowing gasparticle stream an additivethat decomposes at the temperature and pressure of the gas: to releaseammonia or a vaporous amine and form a resinous residue. The additive ispreferably introduced into the gas in an inert carrier liquid. While themethod of this invention has broad general application in reducingcorrosion and erosion of metal surfaces that are exposed toparticle-containing gas streams, it is especially useful in reducingerosion and corrosion of metal drill pipe used in gas drilling wellsinto high-temperature earth formations, such as are encountered in gasdrilling wells into subterranean steambearing formations.

While the exact mechanism by which the method of this inventionameliorates erosion and corrosion is not completely understood, it isbelieved that the ammonia or vaporous amine released when the additiveis heated to a temperature above its decomposition temperature contactsthe metal surfaces exposed to the gas and functions as a corrosioninhibitor protecting these metal surfaces from attack by corrosive andoxidative agents in the gas, and that the non-volatilized portion of theadditive reacts or polymerizes to form a resinous residue that isdeposited in part on the exposed metal surfaces and on the solidparticles suspended in the gas, thereby reducing erosion of the metalparts. However, while the exact mechanism by which the inventionfunctions to reduce erosion and corrosion may not be completelyunderstood, it has nevertheless been demonstrated that erosion andcorrosion of metal parts exposed to a solids-carrying gas stream can beeffectively reduced by the practice of the invention.

Ma'ny'organic compounds exhibit the properties required of the additiveused in the practice of this invention, and additives suitable for useunder specific application conditions can be determined by a simplescreening test, which is hereinafter more fully described. Generally,the organic compounds useful as erosion and corrosion inhibitors aretertiary amines having molecular weights above about 260, and usuallyabove about 300. Organic compounds that have been found particularlyuseful in the practice of the invention are ammonia or amine salts of acomplex tertiary amine containing at least one functional carboxylicacid group.

More preferably, the erosion and corrosion inhibitor used in thepractice of the invention is an ammonium or an amine salt of a complextertiary amine having at least one univalent radical containing afunctional carboxylic acid group with an ester, amine or amide linkage,and the tertiary amine can also contain one or more univalent organicradicals, or a bivalent organic radical which forms a ring structurewith the tertiary nitrogen. These compounds can be convenientlyrepresented by the following generalized formula:

wherein:

R is a univalent organic radical selected from Column 1 of Table 1;

R is a univalent organic radical selected from Column 2 of Table 1;

R is a bivalent organic radical selected from Column 3 of Table 1;

n is 1, 2 or 3;

m is 0, 1 or 2;

p is or 1; and

the sum of n +m+2p equals 3.

Thus, in one preferred embodiment of the invention, the tertiary amineis comprised of a tertiary nitrogen having attached thereto at least oneunivalent organic radical containing a carboxylic acid functional groupselected from Column 1 of Table 1, and the tertiary nitrogen can alsohave attached thereto one or tWo univalent radicals selected from Column2 of Table 1, or a bivalent radical selected from Column 3 of Table 1,which forms a ring structure with the tertiary nitrogen.

TABLE 1 Column 1 Column 2 Column 3 Carboxylic acid Univalent Bivalentradicals radicals radicals R4O0CR;COOH R OOH I|i4 --R4 R0 R C O 0 R11--R4 I R CONH2 -R4N RaCOOH 0 O -R; R4

R4NHCR3COOH N hexane, and the like; and bivalent aromatic radicals suchas 2 phenolethylene, 2,3 diphenoloctylene, paramethylphenol-Z-octylene,1,4 diphenyltetracosylene, bivalent paradiamylbenzene, and the like;

R represents an alkylene containing from 1 to 4 carbon atoms, exemplaryof which are methylene, ethylene, propylene, methylethylene, butylene,and the like;

R represents a bivalent hydrocarbyl radical containing from 1 to 50carbon atoms, and can include bivalent aliphatic, alicyclic and aromaticradicals, specific examples of which are listed in the above definitionof R R represents a univalent hydrocarbyl radical containing from 1 to50 carbon atoms, and can include univalent aliphatic, alicyclic andaromatic radicals; and

R represents a trivalent aliphatic hydrocarbyl radical containing from 1to 4 carbon atoms having a univalent terminal carbon and a bivalentterminal carbon.

Preferred univalent organic radicals containing a functional carboxylicacid group are obtained from the hydrocarbon residue of dimerizedconjugated hydrocarbons containing between about 8 and 44 carbon atoms.Also preferred are univalent organic radicals obtained from conjugatedfatty acids such as linoleic acid, isolinoleic acid, and the like. 7

The carboxylic acid functional groups in the abovedescribed tertiaryamine are neutralized by reaction with ammonia or a water-soluble aminecontaining from 1 to 15 carbon atoms to form ammonium or amine salts ofthe tertiary amine. Exemplary of the amines which can be employed aremorpholine, substituted morpholines having from 5 to 10 carbon atoms,pyrrolidine, pyridine, and simple primary, secondary and tertiary amineshaving the following formula:

wherein R R R are the same or different substituents selected fromhydogen; an alkyl containing about 1 to 4 carbon atoms, exemplary ofwhich are methyl, ethyl, propyl, isopropyl and butyl; an aminoalkylcontaining about 2 to 4 carbon atoms, exemplary of which are aminoethyl,aminopropyl, aminoisopropyl and aminobutyl; and an hydroxyalkylcontaining about 2 to 4 carbon atoms, exemplary of which arehydroxyethyl, hydroxypropyl, hydroxyisopropyl, and hydroxybutyl.

A preferred class of compounds for use in the practice of the inventionare the polyamine salts of an acidic triester of a trialkanol amine,which are generally represented by the following formula:

R400 CRaC 0 OELA N-R4O O CRaGO OH.A.

R40 OCRaCO OH.A

wherein R and R are defined above and A is ammonia or a water-solubleamine containing from 1 to 15 carbon atoms, exemplary of which are theabove-described. amines. In a particularly preferred embodiment R inobtained by esterifying triethanolamine with a long-chain dibasic acidobtained by dimerizing linoleic or isolinoleic acid.

The preparation of polyamine salts of a complex tertiary amine havingthe above generalized formula, as well as other exemplary polyaminesalts which can be used in the practice of this invention, are disclosedin US. Pat. No. 3,151,138, which is herein incorporated by reference.

Organic compounds which possess the requisite properties of decomposingto release ammonia or a vaporous amine and form a resinous residue underspecific application conditions can be identified by a relatively simplescreening test. In accordance with this test, grams of the selectedorganic agent is dispersed in 100 milliliters of water and placed in a250 milliliter reaction vessel. This material is then heated to atemperature corresponding to the application temperature under apressure corresponding to the application pressure. The vapors evolvedare collected and analyzed for the presence of ammonia or amine, and thenature of the residue remaining in the reaction flask is visuallyobserved. Those compounds which release ammonia or a vaporous amine andform a tenacious resinous material under the test conditions can beemployed to reduce erosion and corrosion in a flowing stream of gascontaining dispersed particles of solid material under conditions oftemperature and pressure corresponding to the test conditions.

In the practice of the invention, the organic agent can be injecteddirectly into the flowing gas-particle stream, or alternatively, theagent can be mixed with a carrier liquid and this admixture injectedinto the gas stream. While some or the organic agents useful in reducingerosion and corrosion decompose to release ammonia or a vaporous amineand form a resinous residue at temperatures less than about 200 F., themethod of this invention is most applicable to reducing erosion andcorrosion of metals contacted by a solids-containing gas at atemperature in excess of 250 F., and more preferably in excess of 300 F.

The carrier liquids with which the organic agents are admixed preferablyare relatively inert to the organic agents, are relatively stable at theapplication conditions, and are sufliciently polar to facilitatedispersion of the organic agent in the liquid. Exemplary of the carrierliquids that can be employed in the practice of the invention are water;ammonia; monohydroxy aliphatic alcohols having from 1 to 10 carbonatoms, such as methanol, ethanol, propanol, isopropanol, butanol,hexanol, octanol, and the like; aliphatic amines having from 1 to 10carbon atoms, such as methylamine, ethylamine, propylamine,isopropylamine, butylamine, hexylamine, octylamine, and the like;aliphatic carboxylic acids having from 1 to 10 carbon atoms, such asformic acid, acetic acid, propionic acid, butyric acid, caproic acid,and the like; aliphatic aldehydes having between 1 and 10 carbon atoms,such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, andthe like; ketones having from 1 to 10 carbon atoms, such as acetone andmethyl ethyl ketone, and the like; and mixtures thereof, and especiallyaqueous mixtures thereof. Where the gas into which the additive isinjected contains appreciable amounts of oxygen, such as the case in airdrilling, it is preferred that the carrier liquid be non-flammable toavoid the formation of explosive mixtures.

In general, the organic agent is admixed with the carrier liquid in theproportion of about 0.001 to 25 weight percent of organic agent basedupon the weight of the mixture, and more preferably between about 0.005and about 10 weight percent. Since many of the organic agents andcarrier liquids are slightly acidic, it is preferred that the pH of theliquid dispersions be maintained between about 7 and 12, and morepreferably between about 8 and 11; however, it is recognized that insome instances it may be advantageous to maintain the pH of thedispersion below 7.

The erosion and corrosion inhibiting additive can be prepared at thelocation of use, or alternatively, a concentrated mixture of the organicagent in carrier liquid can be shipped to the site and then diluted withan additional quantity of carrier liquid. Although the additive mixturecan be introduced into the flowing gas stream in any convenient mannerthat provides distribution of the additive in the gas, preferably theadditive is injected into the gas in aerosol form, e.g., the additive issprayed into the gas stream by means of a spray nozzle, or is dispersedinto a separate quantity of gas and this aerosol mixture introduced intothe flowing stream of gas. Erosion and corrosion of the metal partsexposed to a flowing stream of gas containing dispersed particles ofsolid material can be substantially reduced by introducing into the gasfrom about 0.001 to 1 gallon of the above described additive mixture per1,000 standard cubic feet of gas. The exact amount of additive necessaryin any particular application can be determined by laboratory testssimulating the application conditions, or by determining the requiredtreatment by tests conducted under the actual application conditions.However, in either case, it is desired that the quantity of additiveemployed be sufficient to effect a substantial reduction in the erosionand corrosion of the metal parts contacted by the solids-containing gas.

The erosion and corrosion inhibiting method of this invention isparticularly useful in reducing erosion and corrosion of metal partsemployed. in gas drilling wells into high temperature subterraneanformations, such as geothermal reservoirs. .In this application, theadditive is injected into the circulating gas at the surface and passeddownwardly through the drill pipe with the gas. Preferably, the additiveis introduced into the gas in an amount equivalent to about 0.001 to 1gallon additive, i.e., organic agent in the carrier liquid, for each1,000 standard cubic feet of gaseous drilling fluid. Theerosion-corrosion inhibitor can be injected into the circulating mediumat the beginning of the drilling process, however, it is preferred todefer inhibitor injection until the bottomhole temperature of the wellexceeds about 250 F., and more preferably until the bottomholetemperature exceeds 300 F., or even 400 F.

Other agents can be introduced into the drilling gas without adverselyaffecting the performance of the erosion-corrosion inhibitor. Forexample, small amounts of particulate matter can be injected into thecirculating medium to impart desired caking properties to the gas.

Also, a minor amount of an inorganic friction reducing,

agent, such as graphite, molybdenum disulfide, andthe like, can beinjected into the circulating medium. Also, foaming agents can be addedto the circulating gas to improve its capacity for carrying solids fromthe drilling zone to the surface.

The invention is further described by the following examples which areillustrative of specific aspects of the invention and are not intendedas limiting the scope of the invention defined by the appended claims.

EXAMPLE 1 The effectiveness of the method of this invention in reducingerosion and corrosion of drill pipe used in air drilling wells isdemonstrated by a series of well drilling tests. In each test a well isdrilled through a subterranean formation to a depth of between about4,000 and 6,000 feet with a rotary bit mounted on 4 /2 inch drill pipe.Each well traverses several steam-bearing zones. Air is supplied to thedrill pipe from a bank of five primary and two booster compressors at arate of approximately 3,000 standard cubic feet per minute and at apressure of about to 1,250 p.s.i.g. Approximately 21 gallons per hour oferosion-corrosion inhibitor and 2 pounds per hour of finely dividedgraphite are injected into the air employed in drilling wells number 3through 10, the additive injection being commenced when the bottomholetemperature reaches 500 F. No additive is employed in drilling wellsnumber 1 and 2.

TABLE 2 Pipe sections Inhibitor Found un- Replacerate, Observed,satisfactory, ment, factor Well number gallons/hr. number number percentThe addition of the erosion-corrosion inhibitor to the circulatingdrilling gas reduced the erosion, pitting and corrosion of the drillpipe resulting in a substantial reduction in the number of drill pipesections requiring replacement.

EXAMPLE 2 The ability of various complex tertiary amine salts to releaseammonia or a vaporous amine and to form resinous residues at selectedtemperatures is demonstrated by a series of laboratory tests. In eachtest grams of the selected compound is dispersed in 100 ml. of water andplaced in a 250 ml. reaction vessel. The dispersion is heated to apreselected test temperature at atmospheric pressure, and the vaporevolved is collected and analyzed by gas-chromatograph for the presenceof amine. The inhibitor is maintained at the test temperature for onehour, and the nature of the residue in the reaction vessel visuallyobserved. The results of these tests are reported in Table 3.

TABLE 3 Test Amine Test temperapresent Nature of No. Tertiary amine saltture, F. in vapors residue 1 Ethylene diamine salt of 260 Yes Resinous.

TDT 2 N%]%t%lamin0ethanol salt of 390 Yes Do. 3 Morpho line salt of TDT.270 Yes Do. 4... Pyridine salt of TDT 250 Yes Do. 5 Di le igi rl lenetriamine salt of 400 Yes Do. Ammonium salt ofTDT 220 No Do. 7Diethylamino ethanol salt 330 Yes D0.

of TDT. 8 Ntg1 lbuty1amine salt of 230 Yes D0. Dimeylthaminopropyl- 330Yes Do.

amine salts of TDT.

300 Yes Do.

10. N-propylaminoethanol salt of TDT.

1 TDT designates the dimerized linoleic acid triester oftriethanolamine. 3 Ammonia detected in vapors.

EXAMPLE 3 An erosion-corrosion inhibitor is prepared by dissolving equalmolar quantities of 4-morpholine ethanol and suberic acid in an equalvolume of kerosene extract (aromatic extract boiling in the range of400-600" F.), and the solution charged to a jacketed kettle and heatedunder nitrogen blanket to a temperature of 320 F. for six hours, withstirring, by hot oil circulated through the jacket. Completion of thereaction is indicated by an approximate theoretical reduction in theacid value of the reaction mixture. The kerosene is then removed byvacuum distillation and an equal molar quantity of N- butylamine ethanolin aqueous solution added to the residue to produce a tertiary aminehaving the following formula:

CH -CH A portion of the reaction product is heated in a reaction vesselto a temperature of 500 F. at atmospheric pressure. The vapor emittedfrom the reaction vessel is analyzed and found to contain an amine.After heating for one hour, a resinous residue is observed in the bottomof the reaction vessel.

The remainder of the reaction product is dispersed in 5 parts by Weightof ethanol and added to a flowing stream of gas containing abrasivesolid particles, the additive being added to the gas in an amountequivalent to 0.01 gallon per 1,000 standard cubic feet of gas.

EXAMPLE 4 The method of Example 3 is repeated except that the initialreactants are equal molar quantities of Z-diethylamino ethanol and8-carboxy octaneamide. The compound resulting from reaction withN-butylamine ethanol is a tertiary amine having the following formula:

CHZCHZ HO C H (C H )NH-HOO C (CHz)oC ONHCH CH N CHgCH;

The method of Example 3 is repeated except that the initial reactantsare equal molar quantities of 2-heptyl- 2-phenylamino ethanol andS-carboxy-N-meth'yl octylamine. The compound resulting from reactionwith pyridine is a tertiary amine having the following formula:

This reaction product releases a vaporous amine and forms a resinousresidue upon heating to a temperature of 500 F. at atmospheric pressure.

A portion of the reaction product is dispersed in isopropyl alcohol andadded to a flowing stream of gas containing abrasive solid particles,the agent being added to the gas in the proportion of 1 gallon per 1,000standard cubic feet of gas.

While particular embodiments of the invention have been described, itwill be understood that the invention is not limited thereto since manymodifications can be made and it is intended to include within theinvention any such embodiments as Well within the scope of the claims.

The invention having been thus described, we claim:

1. A method for reducing erosion and corrosion of a metal surfacecontacted at an elevated temperature above about 300 F. by a flowingstream of gas containing dispersed particles of solid material, whichcomprises introducing into said gas an organic agent that releasesammonia or a vaporous amine and forms a resinous residue at the elevatedtemperature and pressure of said gas.

2. The method defined in claim 1 wherein said organic agent is admixedwith an inert carrier liquid.

3. The method defined in claim 2 wherein said admixture contains between0.001 and 25 weight percent of said organic agent.

4. The method defined in claim 1 wherein said organic agent is atertiary amine having a molecular weight above about 260.

5. The method defined in claim 4 wherein said organic agent is atertiary amine having the generalized formula:

R is a univalent organic radical selected from Column 1 of Table 1;

R is a univalent organic radical selected from Column 2 of Table 1;

R is a bivalent organic radical selected from Column 3 of Table 1;

n is 1, 2 or 3;

m is 0, 1 or 2;

p is or 1; and

the sum of n+m+2p equals 3.

6. A method for reducing erosion and corrosion of metal surfacescontacted by a high velocity stream of gas having a temperature inexcess of 400 F. and containing dispersed particles of a solid abrasivematerial, which comprises introducing into said gas between about 0.001and 1 gallon of liquid additive per 1,000 standard cubic feet of gas,said additive comprising an inert polar carrier liquid and about 0.001to 25 weight percent of a polyamine salt of an acidic triester of a C toC trialkanol amine, said salt decomposing to ammonia or a vaporous amineand a resinous residue at the temperature and pressure of said gas.

7. The method defined in claim 6 wherein said polar carrier liquid isselected from the group consisting of water and aliphatic alcohols,amines, carboxylic acids and aldehydes containing between about 1 and 10carbon atoms.

8. The method defined in claim 6 wherein said additive is introducedinto said gas as an aerosol.

9. The method defined in claim 6 wherein said inert polar carrier liquidis water and wherein said polyamine salt is a triethylene triamine saltof dimerizcd linoleic triester of triethanolamine.

10. The method defined in claim 6 wherein said polyamine salt has theformula:

CR4O O ORaCOOH.A.

N-C R40 0 CRaCO OI'LA CRiOO CRzCO'OHA wherein R is a bivalenthydrocarbyl radical containing between about 8 and 44 carbon atoms, R;is an alkylene having from 1 to 4 carbon atoms, and A is a water-solubleamine or ammonia.

11. The method defined in claim 10 wherein R is ethylene.

12. The method defined in claim 11 wherein said watersoluble amine isselected from the group consisting of morpholine, pyrrolidine, pyridineand amines having the formula:

wherein R R and R are the same or different substituents selected fromthe group consisting of hydrogen, alkyl radicals containing betweenabout 1 and 4 carbon atoms, aminoalkyl radicals containing between about2 and 4 carbon atoms, or hydroxyalkyl radicals containing between about2 and 4 carbon atoms, and wherein no more than two of said substituentsare hydrogen.

13. The method defined in claim 11 wherein said hivalent hydrocarbylradical is the esterified hydrocarbon residue of a dimerizcd conjugatedfatty acid.

References Cited

